Glad to help you avoid buying a PC! -- Excellent Work!
If you followed the instructions, the /opt folder was originally created by the Linux root user. Then the CFMX install created the coldfusionmx folder tree acting as the cfmx user.
The tar-gnutar process retains the ownership and privileges of the original directory tree.
So, I don't know how the opt folder got locked -- but you resolved it.
AFAIK, the Demo version of open base does not use the /opt folder.
One thing that could have caused problems is this:
In both the Linux and Mac OS X installs, there are several places where you are told to assume the identity of the root user with a su root command. Shortly after you are told to reassume the identity of the cfmx user with a su cfmx command.
It is very important that you not run as the root user unless you need to -- and then reassume a non-root user identity ASAP.
If you don't, bad things can/will happen.
I should have emphasized this in the article!